Recovery of organic liquids used for treating tobacco

ABSTRACT

The recovery of a vaporized organic liquid in a process for expanding tobacco in which tobacco impregnated with the organic liquid is heated to a temperature substantially above the boiling point of the organic liquid with the expanded tobacco being subsequently separated from the vaporized organic liquid. The recovery of organic impregnant is accomplished by collecting and combining impregnant-containing gases from various processing operations, removing entrained solid particles from the combined gas stream by passing through a separator, removing organic impregnant from the gas stream by passing through a bed of activated carbon and reclaiming the organic impregnant from the activated carbon.

United States Patent [1 1 Neel et al.

[ Dec. 25, 1973 1 RECOVERY OF ORGANIC LIQUIDS USED FOR TREATING TOBACCO [75] Inventors: Robert M. Neel; Robert C. Johnson,

both of Winston-Salem, NC.

[73] Assignee: R. J. Reynolds Tobacco Company,

Winston-Salem, NC

22 Filed: June 26, 1972 21 Appl. No.: 266,433

Primary Examiner-Melvin D. Rein Attorney-Albert H. Pendleton et al.

[5 7 ABSTRACT The recovery of a vaporized organic liquid in a process for expanding tobacco in which tobacco impreg- 'nated with the organic liquid is heated to a temperature substantially above the boiling point of the organic liquid with the expanded tobacco being subsequently separated from the vaporized organic liquid. The recovery of organic impregnant is accomplished by collecting and combining impregnant-containing gases from various processing operations, removing entrained solid particles from the combined gas stream by passing through a separator, removing or- [56] References Cit ganic impregnant from the gas stream by passing UNITED STATES PATENTS through a bed of activated carbon and reclaiming the organic impregnant from the activated carbon. 3,612,066 10/1971 Jones et al 131/143 2,722,999 11/1955 Bratzler et al. 55/76 X 3 Claims, 1 Drawing Figure SEPARATOR 6 J9 -T\ HEATER T fzo a 5 9 l 0 E i Z5- '3 1 z ,7

4 V26 IL 2 f7 /6 T TP/PPE z 4 sTEAM g fiol-PE'P EXPANDED 52 JO PRo0uc T CARBON V c E LL 4- v EN T TO v 5 g ATMOSPHERE STEAM Z7 v VENT TO 31 ATMOSPHERE RECOVERY OF ORGANIC LIQUIDS USED FOR TREATING TOBACCO This invention relates generally to treatment of tobacco to increase or expand its filling capacity. More particularly, the invention relates to the recovery of fluids employed in tobacco expanding processes.

US. Pat. No. 3,524,452 to Glenn P. Moser and Grant Mathews Stewart which issued Aug. 18, 1970 describes a method of increasing the filling capacity of tobacco which involves impregnating tobacco with an organic liquid and then subjecting the impregnated tobacco to a stream of hot gas whereby the liquid is quickly vaporized with the simultaneous puffing or expanding of the tobacco particles. The impregnating liquid employed is one which is chemically inert with respect to the tobacco and falls generally into the classes of aliphatic hydrocarbons, aromatic hydrocarbons, alkanols, ketones, aliphatic esters, ethers, halogenated hydrocarbons and mixtures thereof.

Copending application Ser. No. 138,039 filed Apr. 28, 1971, now US. Pat. No. 3,693,631, by Arnold G. Moore and Donald A. Newton relates to a process which is a modification of the process described in the above patent. In accordance with the latter process, tobacco and a stream of vapors of an inert organic compound are introduced into one end of an impregnating zone and moved in concurrent flow relationship to another end of the impregnating zone during which time the tobacco becomes thoroughly impregnated with the compound. After the impregnation has occurred, the merged stream comprising tobacco and the impregnating fluid, including vapors and any condensed impregnant, is withdrawn from the other end of the impregnating zone and suddenly subjected to vapor-expanding conditions whereby the impregnant in the tobacco is vaporized causing the tobacco to expand. The expanding conditions are preferably achieved by rapidly increasing the temperature of the impregnated tobacco by introducing it into a stream of hot gas in the manner described in said US. Pat. No. 3,524,452. The volatile compound or mixture employed for impregnating the tobacco is preferably one which is organic in nature, is chemically inert to the tobacco being treated and has a boiling point at atmospheric pressure between about 50 and +80 C. Preferably, the atmospheric pressure boiling point of the compound is between 40 and +40 C. Illustrative inert organic compounds are: ketones such as acetone and methyl ethyl ketone; aliphatic or cyclic ethers such as methyl ethyl ether, diethyl ether, diisopropyl ether, methyl butyl ether, dimethoxy methane, furan arid tetrahydrofuran; aliphatic alcohols such as methanol, ethanol and 2-propanol; esters such as methyl formate, ethyl formate and methyl acetate; aliphatic hydrocarbons such as butane, pentane, isopentane, hexane and the corresponding unsaturated hydrocarbons; the cycloaliphatic hydrocarbons such as cyclobutane, cyclohexane and cyclopentane; the halohydrocarbons ethyl chloride, propyl chloride, isopropyl chloride, sec-butyl chloride, t-butyl chloride, methyl bromide, ethyl bromide, t-butyl bromide, methylene chloride, chloroform, carbon tetrachloride, ethylene dichloride, ethylidene chloride; and the fluorinated hydrocarbons represented by trichloromotrichlorodifluoroethane and dichlorotetrafluoroethane.

In both the above processes the tobacco after being impregnated with the selected fluid is subjected to vapor-expanding conditions by being withdrawn from the impregnating zone and subjected to a hot gas to vaporize the volatile organic impregnant and to expand the tobacco.

Thus, referring to the drawing which shows in diagrammatic form the flow of various streams, tobacco is introduced into impregnator 2 through feed chute 3. The impregnated tobacco from impregnator 2 is passed into conduit 13 and then into expander 4 in which it is contacted with a hot gas to vaporize the impregnant and to simultaneously expand the tobacco. The expanded tobacco is carried by the hot gas to a separator 6 such as cyclone separator, in which the expanded tobacco separates from the hot expanding gas, vapors of the impregnating fluid and steam vapors. The expanded tobacco is passed through a vapor lock 7 to stripper 8. Residual impregnating fluid is removed by vaporization from the tobacco in steam stripper 8 and the tobacco effluent is passed via belt conveyor 9 to a reorderer 10 in which the product is adjusted to the desired moisture content. The gases (including steam and vapors of the impregnating fluid) are withdrawn from separator 6 through conduit 12, are heated to desired extent in heater l4 and recycled to the expander 4 through conduit 13. A side stream of excess gas consisting principally of vapors of the impregnating fluid, water and some air is withdrawn through line 18 for recovery and recycle. The expanded tobacco emerging from reorderer 10 is routed to bulk storage bin 48.

Most of the impregnating fluid used in the above process is recovered and recycled by subjecting the vapors withdrawn via line 18 to recovery operations which generally involve condensation of the impregnating fluid vapors. When an organic water-immiscible impregnating fluid is employed, this side stream can, if desired, be advantageously processed in accordance with the process described in application Ser. No. 266,416

filed of even date by Robert M. Neel, Clarence Robert Lloyd and Robert C. Johnson. Usually a relatively small but significant amount of the impregnating fluid remains in the tobacco as it passes into stripper 8. For reasons of economy as well as ecology, it is desirable that recovery of the impregnating fluid used in the process be as complete as possible. Unlike the vapors withdrawn through line 18, the vapors associated with the tobacco as it emerges from stripper 8 do not lend themselves readily to condensation of the impregnating fluid due to the low concentrations of such fluid in the vapor stream along with substantial amounts of air. The same is true for vapors emanating from reorderer 10.

Accordingly, it is a principal object of this invention to provide a method for recovering residual quantities of impregnating fluid derived from the expanded tobacco after it has emerged from steam stripper 8. Another object is to recover impregnant vapor from the tobacco feed inlet to impregnator 2.

Briefly, this invention deals with the collection of impregnant vapors escaping from various points in a process of expanding tobacco by impregnating the tobacco with an organic fluid and with the recovery and recycling of the collected impregnant.

Again referring to the drawing, hot expanded tobacco falls onto belt conveyor 9 as it is discharged from stripper 8. Hood 15 is located immediately above conveyor 9 and is designed to cover essentially all of the exposed area of the conveyor between stripper 8 and reorderer 10. Tobacco emerging from reorderer l falls through housing 21 onto vibratory conveyor 23 and is subsequently deposited in bulk storage bin 48. A vapor stream consisting largely of water vapor, air and impregnant vapor is withdrawn from hood and housing 21- by centrifugal fan 16 via conduits 17 and 24, respectively. Both hood l5 and housing 21 must be spaced a sufficient distance from conveyors 9 and 23 to permit air to be drawn into the collecting system without undue entrainment of tobacco particles from the tobacco stream being conveyed. The tobacco particles (primarily fines) which are pulled into the vapor collecting system by fan 16 are removed by passing the vapor stream through a suitable dust collector such as a multicyclone type or sock type. The drawing depicts the use of a multicyclone separator provided with a vapor lock 25 and collecting bin 26. Thus, fan 16 conveys the dust-containing vapor stream to separator 20 via line 19 and the tobacco fines accumulating in bin 26 can be used as desired such as, for example, in the production of reconstituted tobacco sheet.

Fan 16 also withdraws vapors from feed chute 3 and bulk storage bin 48 via lines 52 and 49, respectively. The impregnant vapors in chute 3 result from impregnant escaping through the double vapor lock 53 of the impregnator feed inlet due to the super-atmospheric pressure present in the impregnator under preferred operating conditions. Bulk collection or storage bin 48 is provided with a porous support 50 for the tobacco and a vapor-collecting housingSl immediately below support 50. Porous support 50 is preferably an endless conveyor belt which moves the tobacco to one end of the bin where it is discharged. Fan 16 exerts a slight negative pressure within housing 51 via conduit 49 causing any impregnant escaping from the collected, expanded tobacco to move downward through support 50, through housing 51 and into conduit 49.

The total quantity of vapors collected by fan 16 varies somewhat depending on the amount of tobacco being processed, operating conditions, etc. Each of the conduits connecting fan 16 with the various collection points is provided with a damper or valve to regulate flow rates and to permit most efficient collection of vapor with minimum air intake. Centrifugal fan 27 is also provided with a damper located in line 22 so that a satisfactory balance between fans 16 and 27 is achieved. For a plant processing from 3,000 to 5,000 pounds of tobacco per hour under normal operating conditions, the approximate volumes of vapor collected from the various points are as follows:

Hood l5 1,000 to 1,500 cubic feet per minute at Housing 21 1,000 cubic feet per minute at ambient temperature Feed chute 3 300 cubic feet per minute at ambient temperature Bulk Storage Bin 48 2,000 to 4,000 cubic feet per minute at ambient temperature Typical recovery of organic impregnant based on the above flow rates amounts to about 100 to 300 pounds per hour.

After the combined vapors pass through separator 20 and into line 22, centrifugal fan 27 moves the stream through line 28 to carbon cells 30 or 32 which contain activated carbon. While a single carbon cell of suitable size can be employed, it is preferred to employ two or more such cells to permit continous operation while one of such cells is undergoing regeneration, Based on the flow rates given above, carbon cells containing from 3,000 to 4,000 pounds of activated carbon each will give satisfactory recovery of impregnant.

In a typical operation fan 27 forces the impregnant containing gas stream through line 28 and carbon cell 30 with valves 29 and 34 open and valves 31, 33 and 41 closed. The impregnant is absorbed by the carbon as the gas stream passes through the carbon cell which is vented to the atmosphere by means of valve 34.

When the absorption capacity of carbon cell 30 with respect to the impregnant vapor is reached, the gas stream in line 28 is diverted to carbon cell 32 by closing valve 29 and opening valve 31. Recovery of the ad sorbed impregnant in carbon cell 30 is achieved by closing valve 34 and opening valves 33 and 41. The steam introduced into carbon cell 30 by means of valve 33 displaces the impregnant from the carbon whereupon impregnant vapor and water vapor are forced through line 37 to condenser 44 where condensation of impregnant and water occur. The condensate is collected in tank 40 for further processing and reuse. In the case of trichloromonofluoromethane, for example, the condensate separates into two phases and the heavier organic phase is removed vialine 42 while the aqueous phase is withdrawn through line 45. For water miscible organic impregnants the condensate may be subjected to fractional distillation or extraction with a suitable water-immiscible organic solvent for recovery of the impregnant The present invention is applicable for the recovery of any of the organic fluids used for the impregnation and expansion of tobacco in accordance with the processes as described, for example, in U.S. Pat. No. 3,524,452 and copending application Ser. No. 138,039.

Those modifications and equivalents which fall within the spirit of the invention are to be considered a part thereof.

What is claimed is:

1. In a process for expanding tobacco in which tobacco impregnant with a volatile organic impregnant is contacted with a hot gas to effect rapid'volatilization of the impregnant with concomitant expansion of the tobacco and then the expanded tobacco treated with steam to remove organic impregnant with the expanded tobacco then being reordered to a desired moisture content and finally the reordered expanded tobacco collected, the improvement which comprises collecting organic impregnant-containing vapors normally lost to the atmosphere from the tobacco in a closed system and subsequent to the steam treatment and in the moisture reordering and storing or collecting section, passing sequentially the collected organic impregnant-containing vapors through a separator to remove entrained tobacco particles and through a bed of activated carbon to remove organic impregnant, and thereafter recovering the organic impregnant from said activated carbon bed.

2. A process in accordance with claim 1 wherein the organic impregnant is recovered from the activated carbon bed by displacement with steam and the displaced impregnant subsequently condensed.

3. A process in accordance with claim 1 in which the organic impregnant is-trichloromonofluoromethane.

UNITED STAT-ES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,780,744 Dated December 35, 1923 Inventor(s) Robert M. Neel and Robert C. Johnson It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 4, line 44, "impregnant", first occurrence, should be impregnated Signed and sealed this 9th day of April 197M.

(SEAL) Attest:

EDWARD I-I.FLETCHER,JR. C. MARSHALL DANN Attesting Officer Commissioner of Patents FORM PO-IOSO (10-69) USCOMM-DC 60376-P65 I 0.5. sovnnmnrr rnmrmn OFHCI In! c-au-su 

2. A process in accordance with claim 1 wherein the organic impregnant is recovered from the activated carbon bed by displacement with steam and the displaced impregnant subsequently condensed.
 3. A process in accordance with claim 1 in which the organic impregnant is trichloromonofluoromethane. 